Project 7: Role of Mineral Genesis, Dissolution, and Sorption on Arsenic Fate

与矿物基质相关的砷很少构成直接的环境风险，而在水相中动员的砷则对人类和环境健康构成潜在威胁。因此，控制固体对砷的固存也控制了相关的风险。砷在固水界面发生的化学反应（包括吸附与解吸、沉淀与溶解、还原与氧化）不仅控制着砷向水中的释放，而且构成了除砷技术的基础。因此，该项目期望实现的对关键固水界面上砷行为的基本理解可以应用于砷污染的预防和修复。铁基固体通常用于从受污染的水中去除砷，并且是在自然有氧环境中与砷相关的典型固体。然而，我们目前的工作表明，当放置在厌氧环境时，它们是不稳定的，这是许多含砷废物处理场的典型特征。与硫化物相关的砷则相反，例如在受矿山影响的地点，从厌氧环境向有氧环境的转变刺激了砷的释放。因此，含铁和硫化物矿物在不断变化的氧化还原环境下的行为是提出的工作的主要焦点。该项目的具体目标是确定1)砷与铁固体和2)砷与硫固体结合的机制和途径，并开发3)利用生物和生物地球化学矿物保留过程的工程干预方法，以最大限度地减少固体废物中砷的释放。这些感兴趣的固体-砷-水反应通常是微生物介导的，可能采取多种途径并导致多个最终的固体相

Arsenic associated with mineral matrices seldom poses a direct environmental risk, whereas arsenic that is mobilized in the aqueous phase poses a potential threat to human and environmental health. Consequently, controlling arsenic's sequestration by solids also controls its associated risk. Chemical reactions of arsenic occurring at the solid-water interface (including adsorption and desorption, precipitation and dissolution, and reduction and oxidation) not only govern the release of arsenic into water, but form the basis of arsenic removal technologies. Thus, the enhanced fundamental understanding of arsenic behavior at critical solid-water interfaces that this project expects to achieve can be applied to both prevention and remediation of arsenic contamination. Iron-based solids are typically used to remove arsenic from contaminated water and are the typical solids with which arsenic is associated in natural aerobic environments. However, our current work has shown they are unstable when placed in the anaerobic environments that typify many arsenic-bearing waste disposal sites. The reverse is true for arsenic associated with sulfides, such as at mine impacted sites, where the shift from anaerobic to aerobic environments stimulates arsenic release. Thus, the behavior of minerals containing iron and sulfide when subjected to changing redox environments is the primary focus of the proposed work. The project's specific aims are to determine the mechanisms and pathways for 1) arsenic association with iron solids and 2) arsenic association with sulfur solids, and to develop 3) engineered intervention approaches that utilize biological and biogeochemical mineral retention processes to minimize arsenic release from solid wastes. These solid-arsenic-water reactions of interest are typically microbially mediated and may take multiple pathways and lead to multiple final solid phases with varying capacity for arsenic retention. Because of the complexity of the relevant processes, the project includes experts in aqueous geochemistry, microbiology, chemical dynamic modeling, process engineering and spectroscopy.